Hi, I know that ram can usually be installed with a higher clock speed than what is officially "supported", but that it will downcycle the speed to it's highest supported (ie: 1333mhz) clock cycle. That is providing it's other specs are a match (Ie 240 pin, ddr3, fits to slot on mobo etc...) I have a dell inspiron 580 with motherboard 033FF6 (CPU 1). Officially it only supports 8gb, but works for some up to 16gb using 4x4 configuration. I have a pair of patriot dd3 PC15000 1866MHz ram sticks. WHen installed with the 2 spare slots, the tower refuses to boot, the fan spins and it beeps 4 times. Beep code for 4 is ram issue if I understood. Removing both new sticks allows the PC to boot up normally, removing only 1 of the new 1866mhz ram sticks actually allows the pc to start booting with the startup loading screen and dell logo. At which point it freezes about 1/3rd of the way through it's progress with no error message. I'm wondering why it's having an issue like this instead of just altering the clock speed lower. And why does pulling 1 stick and leaving 1 in allow the pc to start booting at all instead of the beep codes error? Any ideas?